package com.boruan.shengtangfeng.core.utils;

import java.util.List;

/**
 * @author:Jessica
 * @Description:
 * @date:2020年3月10日 上午11:14:10
 */
public class PageUtil {

	/**
	 * 开始分页
	 * 
	 * @param list
	 * @param pageNum  页码
	 * @param pageSize 每页多少条数据
	 * @return
	 */
	public static List startPage(List list, Integer pageNum, Integer pageSize) {
		if (list == null) {
			return null;
		}
		if (list.size() == 0) {
			return null;
		}

		Integer count = list.size(); // 记录总数
		Integer pageCount = 0; // 页数
		if (count % pageSize == 0) {
			pageCount = count / pageSize;
		} else {
			pageCount = count / pageSize + 1;
		}

		int fromIndex = 0; // 开始索引
		int toIndex = 0; // 结束索引

		if (pageNum != pageCount) {
			fromIndex = (pageNum - 1) * pageSize;
			toIndex = fromIndex + pageSize;
		} else {
			fromIndex = (pageNum - 1) * pageSize;
			toIndex = count;
		}

		List pageList = list.subList(fromIndex, toIndex);

		return pageList;
	}

}
